1. Field of Disclosure
This invention relates in general to valve actuating devices, and in particular to methods and systems for locking a valve actuator in an extended position.
2. Description of Related Art
Valves with linear acting stems are commonly used in hydrocarbon drilling and production operations. For actuators used with these valves, a biasing spring often is used to return the valve to a normal position. In some such valves, a pressure media is used in the actuator to move the valve between a normal or contracted, unpressurized position, and an actuated or extended position. The pressure of the pressure media engages a piston to overcome the biasing spring and maintain the valve in the extended position. However, such pressure must be maintained for the valve to remain in the extended position. An unintentional loss of the pressure can cause the valve to return to the normal position, interfering with ongoing operations.
Valves can be locked in an actuated position. However, in the event of a well fire or other high heat and potential dangerous condition, it might be desirable for the valve to return to the normal position. As an example, it can be desirable for the valve to return to the normal position if the normal position will close the valve to reduce environmental and safety risks.